Police in Oklahoma may have gotten a step closer to solving the 1999 mystery of two teenage girls who vanished in the wake of a brutal double murder, as newly discovered investigative notes have shed light on the cold case.

Ashley Freeman and Lauria Bible, both 16, were last seen alive on Dec. 29, 1999, when the girls celebrated Ashley’s birthday with a sleepover at her Welch home.

The next morning, emergency responders, who rushed to the Freeman home after receiving calls about a fire, discovered both of Ashley’s parents, Danny and Kathy Freeman, shot dead, according to the CUE Center for Missing Persons.

The cause of the fire was an accelerant that had been placed near the wood-burning stove, and investigators determined someone had driven down the Freeman’s dirt driveway.

Bible's car was still in the driveway, but the keys were in the ignition. The girls were nowhere to be found.

Law enforcement has spent years scouring for clues in an investigation that spanned nationwide and into Canada and Mexico, but the case has remained unsolved.

But long-lost investigative notes recently found inside an office crate in a police department closet may change all that.

Craig County Sheriff Heath Winfrey was able to provide investigators previously “unknown notes and documents he discovered referencing the Freeman/Bible case that was left from the previous sheriff administration,” Gary Stansill, District 12 District Attorney’s Office investigator, told the Tulsa World.

“These notes and documents have proven to be extremely valuable,” Stansill said. “This information has produced leads that have produced additional leads.”

Stansill did not provide specific details on the leads, but said officials believe there are individuals who have not yet been interviewed who have information about the murders and the disappearances.

Investigators previously looked into the possibility that an intruder or intruders killed the Freemans and the girls were collateral damage.

Their investigation led them to Jeremy Jones, 43, a convicted killer and rapist who once lived in Miami, Okla.

The suspected serial killer said in a confession that he later recanted to the media that he killed the Freemans over an unpaid debt and then set the home on fire, according to the CUE Center for Missing Persons.

When the teens ran out of the burning home, Jones allegedly said he told the girls he was going to help, but instead drove them to Kansas, where he shot them and left their bodies in a mineshaft.

Police found no evidence of their remains in a 2005 search of the area, the Tulsa World reported.

Jones has never been charged in the case and is currently awaiting execution in Alabama in a separate rape and murder.

The Freeman family moved to have Ashley declared dead in 2010, court records obtained by the World said.

Bible's family hopes the development in the case brings them closure, they told the paper.